The present invention relates to an enzyme preparation, which enzyme is an enzyme having an ability to asymmetrically hydrolyze an N-benzylazetidine-2-carboxylic acid ester to preferentially produce an (S)—N-benzylazetidine-2-carboxylic acid, which is a useful production intermediate of pharmaceuticals, and a process for producing (S)-N-substituted cyclic imino acid using said enzyme preparation.
JP-A-2001-46084 discloses a process for producing an (S)-N-substituted cyclic imino acid by asymmetrically hydrolyzing a racemic compound thereof with a separated aqueous enzyme solution, however, said process was not always satisfactory for industrial scale of production in that it was difficult to isolate the produced imino acid from the resulting aqueous phase of the reaction mixture containing the same and amino acids derived from the enzyme solution after completion of the reaction.